I'd check very carefully. I have an X30 which has a miniPCI slot, but does not have an antenna. Some models of the X30 do have internal antenna, but you have to know the specific model number to determine this.
When I gave the model number to IBM (when making the purchase), the CSR didn't realize that it was not supports and I bought the card. It was only after I openned it up did i realize there was no antenna. I contacted IBM again and they eventually figured out that my model did not have an antenna. Fortunately, they had UPS come pick it us and covered shipping both ways.